Seebeck-mediated ionic transport in 1T molybdenum disulfide thin films

Abstract

Molybdenum sulfide (MoS2) is a transition metal dichalcogenide that can achieve ion transport, thanks to its interlayer spacing, 1T/2H surface properties, and inherent thermoelectric properties. In this study, nanosheets of 1T MoS2 were synthesized, deposited as thin film stacks, and utilized as a self-powered nano-channel membrane for the intercalation of sodium chloride ions. Controlled deposition of a NaCl solution droplet onto a thermally activated 1T MoS2 film caused a characteristic voltage spike and decay. These phenomena result from ion–surface interactions followed by Soret- and thermoelectric-induced transport and eventual intercalation within the film layers. Voltage decay curves were recorded for various NaCl droplet concentrations deposited onto MoS2 films subject to a range of temperature gradients (ΔT). Areas under the final decay curves were integrated; both higher salt concentration and greater ΔT were associated with larger integrated areas. A direct relationship between droplet voltage response and concentration was found, potentially allowing for 1T MoS2 to function as a sensor of solution ion concentrations.